The involvement of birds in arbovirus cycles is being studied in relation to a. the capacity of migratory birds to maintain sufficient viremia to implicate them as agents of the spread of the epidemic causing strain VE virus from South to Central America; b. the relationship of avian taxonomic rank to patterns of viremia and antibody production; c. the cycles of little known viruses isolated in Central America and d. the ability of scavengers or carnivores to become infected by feeding on infected prey. Experimental work will be carried out both in the field in Guatemala and in the laboratory. Studies on the long term maintenance of antibodies and of the major gamma globulin components following secondary challenge to an arbovirus are being completed.